While depression is a general disease among mental diseases, since diagnosis is often overlooked and a treatment is not performed, the morbidity rate is high and the patients fall into social-psychological maladjustment. Depression can be mainly classified into a bipolar disease showing radical mood changes, major depression characteristically showing severe depression state but unaccompanied by manic state, and bipolar disorderase and major depression which is more uncertain and mild and does not satisfy a particular diagnosis standard (e.g., dysthymic disorder).
As medicaments effective for the treatment of depression, tricyclic antidepressants (TCA), selective serotonin reuptake inhibitors (SSRI), and monoamine oxidase inhibitors (MAOI) can be mentioned, and many of them increase utilizability of catecholamine (noradrenaline and dopamine) and indoleamine (serotonin) in the central nervous system (CNS). The clinical effectiveness of these medicaments has produced catecholamine-indoleamine hypothesis of depression, and the drug treatment of depression at present is based on this hypothesis.
However, for example, TCA causes side effects, and therefore, EKG and plasma drug concentrations need to be monitored. An adverse influence of SSRI on the sex function (mainly anorgasmia and delayed ejaculation) has been reported. Other general side effects include extrapyramidal-like side effects such as sleep disorder, yawn, changes in body weight, suicidal ideation, dystonic reaction and the like.
Thus, the development of a new therapeutic drug for depression, which does not show harmful side effects that existing medicaments show, but affords an improved effect, has been desired.
On the other hand, the present inventor has reported that phosphatidylcholine shows a cognitive function-improving effect, and a combined use of two particular kinds of phosphatidylcholine is more effective for the improvement of cognitive function (patent document 1). However, it is not known that a combined use of two particular kinds of phosphatidylcholine exhibits a superior anti-depressive action.